Duchess of Cornwall attends a vigil of prayer in Westminster Abbey

A service of solemn commemoration is held Westminster Abbey to mark the
centenary of the start of the First World War before the building's lights
go out one by one until only a burning oil lamp remains at the Tomb of the
Unknown Soldier

The service was held in Westminster Abbey at 10pm - an hour before war was officially declared 100 years ago - a service of solemn commemoration will be held at Westminster Abbey.

Mr Clegg said: "Sixteen million people perished in World War I. It's an almost unimaginable number of people who died in a war which still shapes the world as it is today."

Mr Miliband said: "Young men from across Britain served alongside soldiers from across the world - from the Indian sub-continent to Africa, from Australia to the Caribbean.

"We must also remember those who served their country in other ways, from nurses who risked their lives on the Western Front to those who played their part on the Home Front."

The service included the gradual extinguishing of candles, with an oil lamp extinguished at the tomb of the unknown soldier at 11pm - the exact hour war was declared.

In the same hour, people across the nation switched off lights in places of worship, public buildings, workplaces and homes, and left one light burning as a symbol of hope in darkness.

The project is a reference to then-foreign secretary Sir Edward Grey's famous remark on the eve of the outbreak of war, when he said: "The lamps are going out all over Europe; we shall not see them lit again in our life-time".